Posted
by
samzenpus
on Wednesday December 03, 2008 @06:48PM
from the talk-charging dept.

alphadogg writes "It's possible that in the future conversations on your cell phone could generate enough electrical power to run the phone, without batteries.
That's one possible outcome of recent work by a team of Texas researchers, who appear to have discovered that by building a certain type of piezoelectric material to a specific thickness (about 21 nanometers, compared to a typical human hair of 100,000 nanometers), you can boost its energy production by 100 percent. And the technology could power not just phones, but a whole range of low-power mobile devices and sensors. The breakthrough is an example of 'energy harvesting' that can convert one kind of energy, such as vibrations or solar rays, into electricity."

1000 people screaming only makes one watt? I have no proof of my own, but I'm not so sure on that one. Take two different auditoriums, one with 1000 screaming people in it, and one with a sound system in it.

You're telling me that I could power the sound system with ONE WATT, and duplicate the sound energy of the auditorium that has 1000 people in it?

I need a little more info to see how that would be possible...

Granted, I'm betting that there is something interesting that happens to the piezoelectric

to anywhere near low enough to work with the piezo then you might as well use a very small battery.

Current cell phone technology is perhaps four orders of magnitude away from piezo power. At ten times the piezo power level, say 10mW, you may as well use small cheap batteries. One non-rechargable AAA cell would run for approx 700-800 hours at those levels.

According to my calculations, no battery is required and this article poses an excellent solution, with a few minor modifications and innovations.

If you assume normal human speech is about 60dB. We know dB = 10 log(I/I0) where I0 is 10^-12 W/m^2. So 60dB works out to about 10^-6 W/m^2 -- that's a microwatt per square meter. With 100% efficiency and a mike of 1 cm^2 collecting area, that's around 10^-10 W -- 0.1 nano-watts. (Thanks phliar [slashdot.org] for the calculations.)

Then utilize this energy using recent advances in String Theory, and you have a workable solution.

Because I rarely talk on my phone more than 10 minutes during the course of a month. And I still like to be able to receive calls on a random basis. Voice powered calling is worthless for people that spend that kind of time carrying the phone around rather than talking on it.

A much better solution would be to put something in that converts the jostling motion that handhelds are constantly subjected to into power. Sort of like the old self winding watches.

Talk to CmdrTaco. Of course, it's been this way for about 8 years, so don't expect anything to change. Of course, that doesn't stop them from the Web 2.0 paradigm of replacing a perfectly usable and nice home page design with something eye-gougingly ugly and much harder to use.

Moderations often affect the tone of a message. A misplaced 'Insightful' mod can turn a joke into perceived ignorance. That can lead to negative moderations and a flood of comments trying to dispute it. It's not the most common thing in the world, but I've seen it happen several times.

That's not to say I'm against the idea of a funny comment being modded informative. I do, however, have a preference that people don't use Insightful mods solely to give funny comments karma. And yes, I've softened my stance a bit. Heh.

Oh, thanks a lot for the quick reply! I do now know exactly what you are talking about. Once a post has received one visible mod description, it seems to dictate the way the majority of modders will vote, regardless of the comment's merit.

The reason funny gets modded insightful is because negative mods hurt karma, but funny doesn't add karma. Funny can draw just as much rebuttal as insightful. So if someone says something witty that holds an issue to the light of reason I'll go for the insightful mod.

Sometimes I'll mod something I regard as particularly dense as funny rather than a negative mod. But I laugh at stupid stuff in RL too.

On the other hand, "funny" can now be used as the mod you give to "epic fail" posts (e.g. dead wrong or missed the joke). It can raise those posts up above the trolls for all to see, and open the authors to public embarrassment, all the while failing to reward them with karma. It's really not an unfair use of the moderation system. Who said funny has to mean laughing with the author - can't it mean laughing at the author?

The worst thing is that these people are also damaging the hearing of the person on the other end. Cell phones don't pipe your own voice back at you the way that landlines do. They don't do it because it's not energy efficient and would definitely cause a reduction in talktime. The reality is that a decent phone can pick up what you're saying whether or not you can.

Most modern phones are probably much too power hungry to be get enough energy from audio vibrations, even you manage to ramp up the efficiency close to 100%, which is unlikely to ever be practical.

Where this could be useful is in specialized low-power devices that get bundled into emergency survival [ready.gov]kits.

OTOH, future cellular devices might incorporate enough improvements into power efficiency (e.g., e-ink displays [wikipedia.org]), such that you could significantly extend battery life and perhaps even power a very basic subset of the phone when the battery runs out.

Also, harnessing vibrations efficiently might be very useful in surgically implanted medical devices where replacing the battery can be rather inconvenient [wikipedia.org].

Regarding your last idea, I've interned in the medical device industry so I might have some perspectives... basically, if something like this couldn't power a cell phone it certainly couldn't power sustained operation of a pacemaker! Charge a battery for a defibrillator maybe, but even then you're taking huge risks with rechargable batteries with regard to memory. Basically, even if you were able to use this to increase battery life, you would still decrease *predictability* of the battery life, which is

Yeah, but maybe, in the future, they might find that the convenience of never having to charge your phone is worth more than having the ability to watch TV/videos, browse the web, listen to music, get directions on a map, download ringtones, take pictures, and purchase all kinds of other pointless stuff to do on your phone. We're in a recession afterall, priorities people! Plus I imagine that such a phone would probably be ubersmall and uberlight.

I'm pretty sure that when you have an active call going on a modern phone the radio gear is the most significant power drain especailly if you are a long way from a base station (with radio power required is roughly proportional to the square of distance).

OTOH, future cellular devices might incorporate enough improvements into power efficiency (e.g., e-ink displays [wikipedia.org]), such that you could significantly extend battery life and perhaps even power a very basic subset of the phone when the battery runs out.

IMO, future cellular devices will probably use something based on IMOD display technology [wikipedia.org]. It has all the power benefits of e-ink, but considerably faster switching. They're also already available, albeit at pretty small sizes. There's also color versions of these IMOD displays avaliable, but they also suffer from the current size problems.

The Wikipedia article is somewhat short on the details, so the Qualcomm PR page is here [qualcomm.com]. Like I said, it's really a PR page trying to promote their solution, but the whit

For emergency equipment, wouldn't it be easier and more effective to just put a damn hand crank on the thing? If kids in third world countries can power a laptop with a handcrank I think I can power a phone long enough to call 911.

Where do you get that sort of service? I'm being serious, I live in a big city, but the closest cell phone tower for AT&T to where I live is several miles away. They seem content to only have 2 per the northern half of the city.

Why would you want one? We have watches working off the constant motion of our body/arm/wrist/whatever. Mine takes a few days before it winds down. I think that anyone that stays immobile for that long will not be doing so great in respect of body heat, either.

The harvesting of heat energy always depends on the temperature differential between two materials. The temperature differential between your body and ambient air is so low that it can only be used to produce very, very, very little power. It just so happens that a watch can be designed to run on very, very, very little power--way less than required by a cell phone, you know with its little transmitter and all that kind of stuff;-)

Lets assume that a minimum channel capacity (bits/s) is required to support a conversation, even if we use the absolute best vocoder that eliminates all redundant information. Shannon's Law [wikipedia.org] then says that for a given noise power (set by the environment) there is a minimum signal power which must be transmitted to get error free transmission. Again we are assuming we have an optimal codec, which achieves Shannon's bound. This sets the absolute minimum power consumption of an ideal radio telephone. A real life phone will use more than this. My guess is that this theoretical minimum power is greater than the power which can be harvested from the human voice.

I was thinking the same thing, but the phone would have to be wired for efficient power transmission...either that or it would need a big battery to store all the juice and then return it once it's plugged in to the grid.

It is fully powered by the emanations of the mystical bs! Our marketing departments are now revenue generators (well, generators period)! Hallelujah for bspower! Finally, a cheap and ubiquitous energy source for the masses!

Might you be referring to the joke that went around about 15 years ago (at least that's when I heard it) for keystroke powered word processor. It goes on to extol the virtues of such a machine, providing direct output onto paper, and using only the power of your fingers to run the entire operation. It is, of course, the venerable manual typewriter. I googled but couldn't find the old text of the "Advertisement".

It sounds like talking will just provide a way to charge the phone... it's still going to need some sort of power source to be running when you're not talking into it. Isn't this more like an alternator for a car?

Doesn't much matter. Sound carries *extremely* low power, until you get up into frequencies far, far beyond what people can produce (with their mouths, anyway. Give me a bean burrito, and I might produce watts at 400 kHz).

It does not matter if they improve the microphone efficiency to exactly 100% The amount of power in any reasonable voice is miniscule at best. And most of the power is in the lower part of the register, where the sound wavelengths are several meters long. And to get even a fraction of the power out of a wave, you need a microphone at least a quarter wavelength across.

So even if cell phone microphones were a foot in diameter, they'd only capture a few milliwatts on voice peaks. And cell phones need a couple watts of power full-time to output a watt or so to the antenna. No way, Jose, and by at least three zeros after the "1".

thanks. As a real-world example an old crystal microphone could put out one volt peak-to-peak into one megohm if you talked close. So that's about.3 volts rms, p = e^2/r or 10^-7 watts.So I get 100 nanowatts, close enough.

You'd get 100 x more power from a one square cm solar cell, even from moonlight.

The whole thing makes me sceptical. Especially the author's personal notes he injects, like this gem:

Wang noted that millions of these fiber pairs, each about one centimeter long, would be have to be woven into about 9 square feet of fabric (which would make for a shirt the size of really big poncho)to power an iPod.

9 square feet is a really big poncho? That's a 3x3' square. Most adult sized rain ponchos are well over 3'. Here's one that comes in at 45x53" (over 16.5 square feet) and only covers to waist to elbo. 9 square feet is probably a lot closer to XL T-shirt size than it is poncho size.

If the guy has issues comprehending something as simple as the size of 9 square feet, how can we trust him with the more complex

A little googling found that: a cell phone requires something on the order of 1W (while in use). Speaking in a normal voice produces on the order of 0.00001W of sound energy. I don't think cell phone power requirements could ever get that low (unless the cell towers were much closer together). Interesting idea, though.

yeah, if you force my law to use this technology as an implant in all teenage girls, you can basically eliminate the need for coal/fossil fuel/nuclear fuel/etc in power plans of north america as a whole.

Some back-of-the-envelope calculations: normal human speech is about 60dB. We know dB = 10 log(I/I0)
where I0 is 10^-12 W/m^2. So 60dB works out to about 10^-6
W/m^2 -- that's a microwatt per square meter. With 100% efficiency
and a mike of 1 cm^2 collecting area, that's around 10^-10 W
-- 0.1 nano-watts.